The first rule of Fight Club is that you don't talk about Fight Club. And the same can likely be said for pretty much any undercover investigation at the FBI.So when Mike blabbed to Paige about his investigation into Briggs ...

The first rule of Fight Club is that you don't talk about Fight Club. And the same can likely be said for pretty much any undercover investigation at the FBI.

So when Mike blabbed to Paige about his investigation into Briggs on last week's episode of Graceland, it's safe to say he broke a few rules. "That is a very, very big thing and that changes everything," star Aaron Tveit tells TVGuide.com. "That was the first moment we see weakness in Mike."

After getting stabbed by the notorious Jangles - aka the key man - and waking up in a hospital bed, a morphine-induced Mike told Paige (Serinda Swan) that he was placed in the house to look into fellow FBI agent and house leader Briggs (Daniel Sunjata). "He really feels like he's a man without a country in that moment," Tveit says. "Mike didn't just want to say, 'I'm here to investigate Briggs.' In my head, he was trying to say, 'I'm here to investigate Briggs, but this has happened and I need all your help. I don't know what to do.'"

Unfortunately, Mike got no such guidance from Paige, who quickly left Mike's hospital room. In Thursday's episode (10/9c, USA), Mike will have to deal with the fallout of his bedside confession. "The beginning of this next episode, Mike walks into the house and he has no idea who she's told what, if she said anything, if everyone knows, if no one knows," Tveit says. "He has no idea what he's walking into."

However, after checking himself out of the hospital against doctor's advice, Mike won't be home on disability for long. In addition to going undercover in prison to keep close to Bello (Gbenga Akinnagbe), Mike's investigation into Briggs will take a dramatic turn. In the wake of the murder of his controlling officer, Juan (Pedro Pascal), Mike will have to answer to a much higher power - the Regional Director of the Southern California FBI. "Juan, in a way, was misleading Mike and had his own vendetta. Mike's reports weren't being shared with the FBI - they've only seen some of it. So Mike now has to reassert himself with this person, who is actually one of his big bosses," Tveit says. "Now Mike is really getting an assignment so it gets even more intense and more official."

Page 2 of 3 - That assignment will also get decidedly tougher as the clues begin to come together about Juan's murder. As viewers saw last week, Juan dressed as Jangles to try to elicit a confession from Briggs, whom Juan believed had previously killed several FBI agents. However, a drunken Briggs murdered Jangles to protect himself. "That is definitely going to come up and really put a wrench into things," Tveit says. "The FBI is going to come to Mike with their theory about what happened to Juan, and that's going to blow this thing wide open."

So what will Mike do if, or when, suspicions turn to the man who has now saved his life twice? "I never thought that Briggs was a bad guy, as Aaron reading it, and as Mike. I just made the decision that I never thought Briggs was an evil person. He just got into these circumstances and he was basically trying to get through it and overcome these other agents being killed," Tveit says. "From my perspective, no matter what happens with Briggs - if Mike needs to bring him in, if the evidence is there - Mike is trying to get this guy help because he is his friend and he does respect him and he does care about him."

But how far is Mike willing to go to save his friend? Tveit admits that Mike's idea of right and wrong has changed dramatically since he was first placed in Graceland. "He's also learned a lot from Briggs that, to be a good undercover agent, it can't be all by the book," Tveit says. "As we get to the end of the season and hopefully move forward, I'm hoping that Mike has learned that sometimes you do have to bend the rules and work in that grey area and be OK with it."

Although Tveit jokes that Mike will need "to go to therapy about five years from now" to deal with some of the brutal things he's seen as an undercover agent, such as Eddie's suicide, Graceland may now be more than just a temporary assignment for Mike. "At the end of the season, certain things are going to happen, and I think he's going to have to reevaluate what he really wants and what he really sees for himself," he says. "He's discovered that he's actually good at this and that he can hack it as a field agent and has a certain skill set that really lends itself to this undercover game."

Page 3 of 3 - Maybe even, Tveit hopes, as Briggs' full-time partner. "Not to make it like some buddy thing, but I think he and Briggs are a great team," he says. "If Mike does end up at Graceland for a long time, hopefully Briggs is there too. Mike probably knows that, once they figure all this stuff out, they can probably do a lot of good together."